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From: "cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug dynamic-link/31501] _dl_tlsdesc_dynamic_xsavec may clobber %rbx
Date: Tue, 19 Mar 2024 02:46:16 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D31501

--- Comment #7 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by H.J. Lu <hjl@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=3Dglibc.git;h=3D717ebfa85c8240d32d0=
d19d86a484c31c55c9617

commit 717ebfa85c8240d32d0d19d86a484c31c55c9617
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Mon Mar 18 06:40:16 2024 -0700

    x86-64: Allocate state buffer space for RDI, RSI and RBX

    _dl_tlsdesc_dynamic preserves RDI, RSI and RBX before realigning stack.
    After realigning stack, it saves RCX, RDX, R8, R9, R10 and R11.  Define
    TLSDESC_CALL_REGISTER_SAVE_AREA to allocate space for RDI, RSI and RBX
    to avoid clobbering saved RDI, RSI and RBX values on stack by xsave to
    STATE_SAVE_OFFSET(%rsp).

       +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D+<- stack fra=
me start aligned at 8 or 16 bytes
       |                  |<- RDI saved in the red zone
       |                  |<- RSI saved in the red zone
       |                  |<- RBX saved in the red zone
       |                  |<- paddings for stack realignment of 64 bytes
       |------------------|<- xsave buffer end aligned at 64 bytes
       |                  |<-
       |                  |<-
       |                  |<-
       |------------------|<- xsave buffer start at STATE_SAVE_OFFSET(%rsp)
       |                  |<- 8-byte padding for 64-byte alignment
       |                  |<- 8-byte padding for 64-byte alignment
       |                  |<- R11
       |                  |<- R10
       |                  |<- R9
       |                  |<- R8
       |                  |<- RDX
       |                  |<- RCX
       +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D+<- RSP align=
ed at 64 bytes

    Define TLSDESC_CALL_REGISTER_SAVE_AREA, the total register save area si=
ze
    for all integer registers by adding 24 to STATE_SAVE_OFFSET since RDI, =
RSI
    and RBX are saved onto stack without adjusting stack pointer first, usi=
ng
    the red-zone.  This fixes BZ #31501.
    Reviewed-by: Sunil K Pandey <skpgkp2@gmail.com>

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